> For the complete documentation index, see [llms.txt](https://merithic.gitbook.io/merithic-docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://merithic.gitbook.io/merithic-docs/api-reference/endpoints/check.md).

# POST /check

The simplest licensing call. Returns whether a player holds an active license.

```
POST https://api.merithic.com/check
```

## Request

| Field        | Type             | Required | Description                             |
| ------------ | ---------------- | -------- | --------------------------------------- |
| `user_id`    | string or number | yes      | The Roblox user ID of the player.       |
| `product_id` | string           | yes      | Your product's ID, from the dashboard.  |
| `key`        | string           | yes      | The buyer's license key.                |
| `game_id`    | string or number | no       | The place ID, recorded for your alerts. |

```json
{
  "user_id": "123456789",
  "product_id": "prod_abc123",
  "key": "the buyer's key",
  "game_id": "987654321"
}
```

## Response

```json
{ "success": true }
```

`success` is `false` when there's no license, it's paused, or the key doesn't match the one issued to that user. The endpoint always returns `200`; a `false` result is an answer, not an error.

{% hint style="danger" %}
**Do not gate anything valuable on this alone.** The response is a plain boolean, so anyone who can intercept the request can return `{ "success": true }` and walk straight past it.

Use [`/unlock`](/merithic-docs/api-reference/endpoints/unlock.md) for anything you actually care about protecting. `/check` is for cheap, non-critical checks like showing UI state.
{% endhint %}

## Examples

{% tabs %}
{% tab title="Luau (server)" %}

```lua
local HttpService = game:GetService("HttpService")
local Players = game:GetService("Players")

local PRODUCT_ID = "prod_abc123"
local KEY = "the buyer's key"

local function isLicensed(userId: number): boolean
	local ok, res = pcall(function()
		return HttpService:PostAsync(
			"https://api.merithic.com/check",
			HttpService:JSONEncode({
				user_id = tostring(userId),
				product_id = PRODUCT_ID,
				key = KEY,
				game_id = tostring(game.PlaceId),
			}),
			Enum.HttpContentType.ApplicationJson
		)
	end)

	if not ok then
		-- Network failure. Decide deliberately: this fails CLOSED.
		return false
	end

	local body = HttpService:JSONDecode(res)
	return body.success == true
end

Players.PlayerAdded:Connect(function(player)
	if not isLicensed(player.UserId) then
		warn(("%s is not licensed"):format(player.Name))
	end
end)
```

{% endtab %}

{% tab title="Node.js" %}

```javascript
async function isLicensed(userId) {
  const res = await fetch("https://api.merithic.com/check", {
    method: "POST",
    headers: { "Content-Type": "application/json" },
    body: JSON.stringify({
      user_id: String(userId),
      product_id: "prod_abc123",
      key: process.env.UPDATR_KEY,
    }),
  });

  if (!res.ok) throw new Error(`check failed: ${res.status}`);
  const { success } = await res.json();
  return success === true;
}
```

{% endtab %}

{% tab title="curl" %}

```bash
curl -X POST https://api.merithic.com/check \
  -H "Content-Type: application/json" \
  -d '{
    "user_id": "123456789",
    "product_id": "prod_abc123",
    "key": "the buyers key"
  }'
```

{% endtab %}
{% endtabs %}

## What the seller sees

If a key is used under a **different** user ID than the one it was issued to, the call fails and a **leaked key** alert appears on the seller's dashboard. That's how key sharing gets caught, so don't reuse one key across accounts while testing.

## See also

{% content-ref url="/pages/s4HsRum87vgVH4KC5lHW" %}
[POST /unlock](/merithic-docs/api-reference/endpoints/unlock.md)
{% endcontent-ref %}


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